This invention relates to a knock-type propelling pencil, and more specifically relates to such a propelling pencil as which prevents breaking of a lead by resiliently absorbing the force transferred to the lead when an excessive pressure is applied to the pencil lead.
A conventional propelling pencil as shown in FIG. 1 has heretofore been proposed, in which structure to prevent breaking of a lead has been provided.
In FIG. 1, reference numeral 1 is a holder, reference numeral 2 is a lead storing cylinder which is inserted into the holder 1 slidably in the direction of the holder axis, reference numeral 3 is a lead chuck fixed in the tip of the lead storing cylinder 2, reference numeral 4 is a chuck ring loosely fitted to the tip of the lead chuck 3. Further, reference numeral 5 is a sleeve disposed between the chuck ring 4 and the holder 1 and slidably inserted into the lead chuck 3, and in the rear portion of the sleeve 5, a spring 7 is disposed between the rear portion and the stopper 8 within the holder 1.
The spring 7 is disposed in such a manner that breaking of a lead is prevented by absorbing of resulting in motion applied to a lead, when the lead chuck 3 has applied thereof an excessive pressure in the use of the pencil. The sleeve 5 is also provided with the another spring 6 mounted about lead chuck 3 and provided to actuate the aforementioned lead storing cylinder 2 in the return direction.
Now, assuming that the knocked portion (not shown) in the end of the lead storing cylinder 2 is pushed, the lead storing cylinder 2 is moved to a direction against the actuating force of the spring 6 to open the lead chuck 3, and the lead 1b projects out of the tip of the cap 1a to a in the predetermined length. In the condition of writing operation, if excessive lead pressure is added thereto, the sleeve 5 is moved backward through the lead chuck 3 against the actuating force of the spring 7. Accordingly, the excessive lead pressure is absorbed resiliently so that breaking of a lead will be prevented.
However, since this prior art construction requires that the sleeve 5 be formed out of a metal pipe in which the spring 7 is provided, some defects arise due to difficulties in manufacture and assembly and also result in high material costs.